The present invention relates to a container for securely carrying a substrate such as a reticle, mask, wafer, or the like. More particularly, the present invention relates to a container that may be used to store the substrate when not in use or that may be used to contain the substrate for transport.
Semiconductor manufacturing processes involve the use of reticles, masks and wafers which generally take the form of a substantially planar substrate. During the manufacture of semiconductor devices, small particles of foreign material may settle upon the particular substrate and damage the substrate or interfere with a manufacturing process. Great efforts are made to filter all particles from the environment in which semiconductor devices are manufactured and to prevent particles from contacting substrates. A continuing challenge in the industry is to remove smaller and smaller particles, even sub-micron sized particles, from the manufacturing environment and the associated equipment and to eliminate the introduction of particles into the environment from the equipment itself.
Prior devices minimized the settling of particles upon substrates by providing a container that was capable of housing the substrate. U.S. Pat. No. 4,422,547 to Abe et al., for example, described a container comprising a housing body that included an opening for receiving a substrate, a door for closing the opening, and means for fixing the received substrate in the container. The means for fixing the received substrate included a contact member for contacting the upper surface of the substrate to press it against a support surface in the housing when the door was closed. The contact member was adapted to retract to release the substrate when the door was opened. While the Abe et at. container prevented particles generated externally from settling onto the substrate, the device itself generated particles within the container which settled upon the substrate.
Some of the particles generated within the Abe et at. device were produced by the mechanism for fixing the substrate in the container. The mechanism for fixing the substrate in the container included a stainless steel member which rotated within bearings formed in the lid of the container above the substrate. The rotation of the stainless steel member within the bearing generated particles which fell directly upon the substrate. Further, because the contact member contacted the upper surface of the substrate, the contact member itself transferred particles directly to the substrate. Also, because the means for fixing the substrate in the container did not fully prevent relative motion between the substrate and the housing, particles were generated when the substrate rubbed against the container housing. These particles could settle on the substrate.
Improvements were made to the prior devices in an attempt to prevent relative motion between the substrate and the container. Such improvements included placing a silicone material on a ledge formed in the housing upon which the substrate rested. However, the silicone material did not entirely prevent relative motion between the substrate and the housing.
Another concern in constructing a container for a substrate is static electrical charge. Substrates are susceptible to electrical discharge. Even small quantities of electrical charge may create high voltages across portions of the substrate possibly destroying or damaging portions of the substrate and rendering the complete substrate useless. Therefore, it is desirable to house the substrate in a container that prevents electrical charge from propagating to the substrate.